Question

我需要在我的服务器上收到一个大的JSON（超过22个字段）。我有一个包含很多字段的案例类：

case class Filters(objectType: Option[String] = None,
     deal: Option[String] = None,
     roomsCount: Option[String] = None,
     region: Option[Int] = None,
     district: Option[Int] = None,
     direction: Option[Int] = None
     ...
)

控制器中的JSON格式功能：

implicit val filtersFormat = Json.format[Filters]

编译时我遇到错误：

[error] WebSockets.scala:18: No unapply or unapplySeq function found
[error]   implicit val filtersFormat = Json.format[Filters]
[error]                                          ^

有没有办法在不将JSON分解为小部件的情况下解决问题？

Answer 1

正如@Sawyer提到的，您可以使用external library。摘自this blog。

首先将lib依赖项添加到您的SBT

libraryDependencies += "ai.x" %% "play-json-extensions" % "0.42.0"

然后您可以像这样使用它：

import ai.x.play.json.Jsonx
import play.api.libs.json.{Json, OFormat}

case class Foo(a1: String, a2: String, a3: String, a4: String, a5: String,
               a6: String, a7: String, a8: String, a9: String, a10: String,
               a11: String, a12: String, a13: String, a14: String, a15: String,
               a16: String, a17: String, a18: String, a19: String, a20: String,
               a21: String, a22: String, a23: String)

object Foo {
  implicit val f: OFormat[Foo] = Jsonx.formatCaseClass[Foo]
}

Answer 2

我是这样做的：

case class Filters(part1: Part1, part2: Part2, ...)

case class Part1(
    field1: Field1,
    field2: Field2,
    ...
    field10: Field10,
)

object Part1 {
    implicit val part1Format = Json.format[Part1]
}

...

object Filters {
    implicit val filtersReads = (
        JsPath.read[Part1] and
        JsPath.read[Part2] and
        ...
    )(Filters.apply _)

    implicit val filtersWrites = (
        JsPath.write[Part1] and
        JsPath.write[Part2] and
        ...
    )(unlift(Filters.unapply))
}

Answer 3

也可以选择手动执行，而不是使用格式，读取或写入：

implicit object JsFormatter extends Format[Filter] {

  private val tagField1 = "field1"
  private val tagField2 = "field2"
  private val tagField3 = "field3"
                ...
  private val tagFieldN = "fieldN"   // N > 22

  override def reads(json: JsValue): JsResult[Filter] = JsSuccess(
    Filter(
      (json \ tagField1).as[Long],
      (json \ tagField2).as[Int],
      (json \ tagField3).as[String],
                  ...
      (json \ tagFieldn).as[Boolean]
    ) 
  )

  override def writes(filter: Filter): JsValue = Json.obj(
    tagField1 -> filter.field1,
    tagField2 -> filter.field2,
    tagField3 -> filter.field3,
              ...
    tagFieldN -> filter.fieldN
  )
}

我们有很多从22列传递的案例类，所有案例类都可以正常工作而不会将它们分成几部分。

Answer 4

我有相同的铅，并通过使用找到解决方案

Jsonx.formatCaseClass[Filters]

可以找到解说词 https://harrylaou.com/playframework/bigjson/

Play Framework Scala格式大JSON（找不到unapply或unapplySeq函数）

4 个答案: